A Study Evaluating B Cell Levels In Infants Of Lactating Women With CIS Or MS Receiving Ocrelizumab

Inclusion Criteria: * Woman is between 18 and 40 years of age at screening * Woman is willing to breastfeed for at least 60 days after the first post-partum ocrelizumab infusion (this decision is to be taken prior to and independent from study participation) * Woman is willing to provide breastmilk samples * Woman has a diagnosis of MS or CIS (in line with the locally approved indications) * Woman has delivered a healthy term singleton infant (≥37 weeks gestation) * Infant is between 2-24 weeks of age at the time of the mother's first post-partum dose of ocrelizumab * For women who received commercial ocrelizumab (OCREVUS) before enrolment: documentation that last exposure to ocrelizumab occurred more than 3 months before the last menstrual period (LMP) and was given at the approved dose of 2 x 300 mg or 1 x 600 mg * Woman agrees to use acceptable contraceptive methods during the study Exclusion Criteria related to the Mother: * Hypersensitivity to ocrelizumab or to any of its excipients * Received last dose of ocrelizumab \<3 months before the LMP or during pregnancy * Active infections (may be included once the infection is treated and is resolved; women with bilateral mastitis infection should not have samples collected until the infection is completely resolved) * Prior or current history of primary or secondary immunodeficiency, or woman in an otherwise severely immunocompromised state * Known active malignancies, or being actively monitored for recurrence of malignan…